A pressure regulator is a valve that controls fluid flow from a high pressure source to a low pressure device. Pressure regulators are utilized for various applications including, but not limited to, facilitating the delivery of gas or liquid to a device such as a laser, fuel cell or welding system, for example. The general operation of a pressure regulator and its integral components is described in U.S. Pat. No. 5,381,819, which is incorporated by reference in its entirety.
In a regulator having a valve plug and valve spring arrangement, such as the regulator illustrated in patent application Ser. No. '365, one end of the valve plug, referred to as a stem, travels within an aperture formed in the regulator housing and the other end of the valve plug cooperates with a valve seat to open and close the regulator. The valve plug mates and seals with the valve seat in a “no-flow” state to prevent flow through the regulator. Conversely, the valve plug is sufficiently separated from the valve seat in a “full-flow” state to permit maximum flow through the regulator.
In a “low-flow” state, the valve plug is only slightly separated from the valve seat. The slight separation is sufficient to permit a small volume of fluid to pass between the plug and the seat. Two flow vortexes form on either side of the valve plug which vibrate the valve plug. Since only a slight distance separates the plug and the seat, the vibrating plug repetitively strikes the valve seat. The resulting contact damages the valve plug and the valve seat and generates an undesirable audible noise.
More specifically, the repetitive contact degrades the exterior surfaces of the valve plug and valve seat, thereby diminishing the sealing capacity between the valve plug and the valve seat in the closed position of the regulator. In order to limit the vibration of the plug and eliminate the destructive contact between the valve plug and valve seat, a light interference fit is commonly required between the valve plug stem and the aperture disposed in the regulator housing. Accordingly, the size tolerance of both the housing aperture and the valve plug stem are tightly controlled. In fabrication, such excessive tolerance control may be relatively expensive, difficult to maintain and onerous to inspect.
Thus, there is a need to reduce the noise and damage resulting from the aforementioned valve plug arrangement, while minimizing costs.